1. Field of the Invention
The present invention relates to a magnetic head-slider assembly used in a magnetic disk apparatus for recording and reading back information on a magnetic disk. The head-slider assembly has improved stiction properties.
2. Description of the Background Art
A conventional structure for a magnetic slider is shown in FIG. 1a. The slider (100) has a leading surface (101), a trailing surface (102), and an air bearing surface which resides next to the disk and has a magnetic read/write element (103). As used herein, the air bearing surface of a slider shall mean the entire surface of the slider which faces the disk during operation of the disk drive. The air bearing surface usually has a upper portion (104) very close to the disk and a lower portion (106). A cross-sectional view of the trailing edge of the slider is shown in FIGS. 1b and 1c. In some sliders, the trailing surface is normal to the air bearing surface as shown in FIG 1b. In some cases, a single step (105) is formed in the air bearing surface as shown in FIG. 1c in order to better control the airflow of the air bearing or as an artifact of the manufacturing process.
The trailing edge of the slider is susceptible to accumulation of lubricant and hydrocarbon materials during the operation of the disk drive. The accumulated material can then interfere with the normal flying of the slider, generally increasing the spacing between the sensor and the disk. This increased spacing can result in a high error rate when data is retrieved from the disk. The spacing can also be reduced leading to accelerated wear. The accumulated material can also migrate back into the area of the air bearing surface when the slider comes to rest on the disk and thus increase the stiction forces at the air bearing surface during subsequent startup operation.
Stiction results from the accumulation of lubricant or hydrocarbon contaminants on the trailing edges of sliders that are flown over disks for prolonged periods of time. When the disk drive is turned off and the head comes to rest on the disk, the liquid materials can flow beneath the slider causing the slider to stick to the disk. This stiction force, if severe, can prevent the disk from starting again. As an example, if a liquid covers 2000 xcexcm2 of area on the air bearing surface, the effective stiction force can be 40 gm. The force is reported here as grams equivalent. The force in units of dynes can be obtained by multiplying by the acceleration of gravity. This propensity of liquids to accumulate on the trailing edge of the slider generally is more pronounced as the spacing between the flying slider and the disk is reduced. Future disk drives will have reduced spacing between the slider and the disk in order to increase areal density. For future designs requiring very high densities, the slider will be in frequent contact with the disk. Accordingly, the propensity of the slider to accumulate material at the trailing edge will increase for future applications. Thus, the stiction is a problem now and will be more pronounced in the future.
It is the object of the present invention to provide a novel slider structure which greatly mitigates these problems with stiction. Other objects and advantages will be apparent from the following description.
A general object of the present invention is to provide a slider which greatly reduces the stiction forces associated with the material buildup on the trailing edge of the slider.
According to the present invention, multiple steps are formed at the intersection of the trailing edge and the air bearing surface of the slider. These multiple steps result in unexpectedly large reductions of stiction forces and also reductions in the accumulation of extraneous material on the slider. In one embodiment of the invention, two or more steps are formed at the trailing edge of either a side element or a center element slider. The trailing edge is defined as the intersection of the air bearing surface and the trailing surface. In another embodiment of the invention, the steps are formed in the trailing edge of a side element or a center element slider where the steps are formed across the entire trailing edge of the slider. In an alternative embodiment, the steps extend across the trailing edge of the slider except in the near proximity of the read/write element. In another embodiment, a disk drive apparatus is described where the disk drive comprises a disk, suspension, and slider wherein the slider has a plurality of recessed steps in the air bearing surface at the trailing edge.